Hydraulic cycle control



Patented Aug.1'5,19 39 I UNITED STATES HYDRAULIC crow com nupii ii. Mlller and win a. Morris, Detroit, men,

pressure motors, and is of particular value in connection with such motors as are used on hydraulically operated machine tools, and the like.

Machine tools have been provided with double acting fluid pressure cylinders and pistons for actuating reciprocating work or tool holders during the operation of the machine. In priorinf 1 stallations means are provided for shifting the in- .take and exhaust valves, to reverse the piston,

and such means usually comprise some sort of mechanical trip mechanism which is actuated by means associated with the'piston, as'the latter approaches .the end of its stroke. It has been found that for some classes 0! work such a mechanism does not give a sufllciently positive and accurate stop for the piston in its operative movement. Accordingly, it is one of the objects of this invention to provide a reversing means for a fluid pressure motorwhich will provide a positive and flxed point of reversal in the motors cylcle of movement. p

A more limited object is to provide a reversing means for a fluid pressure motor of the type deversing a reciprocatory fluid pressure motor at a fixed point in its path oi movement, which means] is controlled by the fluid pressure within the motor itself.

'Another object is to provide means to actuate the reversing valve of a fluid pressure motor upon a drop in the exhaust pressure at one side 01 said motor incident to the completion of its exhaust stroke.

Other objects and advantages of the invention will become apparent'from the attached specification, the accompanying drawing and the ap- ,pended claims.- i

The drawing illustrates, partly diagrammatical y, a preferred form of the invention, the essential elements thereof being illustrated in section- In the. drawing there is shown at l the cylinder 01' a hydraulic motor, which includes apiston2 and piston rod 3. The piston rod 3 may be ad- Jnstably connected .to a reciprocating work or tool holder, not shown, of a machine tool. Such a machine may, for example, be a drill press having a reciprocating drill head which is adiustably connected to the piston rod.

The cylinder I has a removable head 4 secured in place by suitable studs 5. The opposite end of the cylinder is formed at B to receive a conventional packing gland 1 having a packing 8 for preventing leakage around the piston rod. The

60 interior end wall 9 is flat and is adapted to engage scribed which is effective only after the movable assignors to Huxon Holding Corporation, a corporation oi Mlehla'an Y [Application July 1m, No. 92,382

4cm (ci."isi iti This invention relates to reciprocating fluid abutment I on the piston when the latter reaches the limit oi! its movement in the working direction. .A similar abutment ii is provided at the opposite face of the piston,'and piston rings i2 are fltted into conventional ring grooves about the periphery of the piston. The walls of the cylinder adjacent its forward end are provided with v a pair of ports. II and I4, while similar ports II and it are provided adjacent the opposite end ofthe cylinder. These ports are'threaded or otherwise adapted to receive suitable fluid conduits II, II, II and 2|, respectively.

Each of the conduits n and leis adapted to g operate either as a pressure or exhaust conduit for the end of the cylinder to which it is' connested. These functions are controlled by a reversing valve, indicated generally at 2|, which is interposed in lines I! and 1|. The reversing valve 2! comprises a casing 22 closedjat one endandi having at the opposite end thereof a removable closure plate 23 secured in place. by studs 24.. Plate 23 is provided with an opening ior thereception of a packing gland 28 and a valve rod 26,,

21 on its inner end. The valve housing 221s. proextends through the opening and has a valve head,

the conduits I! and II are threaded into the ports 2| and 2|,-respective1y. Port 3| communicates with a conduit 13 whicls'is connected to the discharge side oi a pump 34,'wliile ports 3| and 32 communicate through conduits II and 38 with'an atmospheric pressure storage reservoir 31. 'I'he intake of pump 34 is connected to reservoir 81 by a conduit 3|.

A valve operating lever is is slotted at its'end 4| to receive the end of valve rod 24 and the end of the rod is threaded to receive a pair of nuts 4| and 42 which are adapted to engage opposite sides of the end oi'the lever. The lever 39 is pivoted at 4| to a fixed portion oi. the machine.

' assumes in the drawing. However, upon return movement of the piston downward as viewed in the'drawing, cam 41 will pass beyond roller 46 I without changing the position of lever 39.

The lever 39 is apertured at 50 to receive a piston rod ii 01 an actuating motor comprising a cylinder 52 and a piston 53 having abutments similar to those on the piston 2. This cylinder' has a removable closure plate 54 at one end thereof, held in place by studs 55, and at the go ciprovid an appreciabl 7 7o bressuite ii eflectedby reasontoi the is f js i ihemem opposite end is provided with a. packing gland; that the piston. 53 will remain at its uppermost 56 for the reception oi! piston rod ii. The upper position until the resistance to movement 01 pisend of cylinder 5; isir constant communication tom 2 exceeds the maximum resistance that will s with the (end;M 1thefltipeletiiifi(tidbit! e oiferled' by ,thegtool= .durir gmprmal' 5 ,through conduit :0. Secured tomn extehsib Theabovedscrib'd coiiditfdii willpeontinue to 5 1 ot rod ii is a compressible abutment member exist so long as piston 2 continues its "movement "comprising a pair or telescopic housings 58 and z -fieowm the lower end of cylinder I. However, 50, within which is a. coiled compressiop spripg whenpiston reaches and abuts the end of its I, A nut ii threaded on the end bfibdil"is"'fcylinder;of'iihvother positive stopthat may be 1 10 provided for retaininzthis vided iiu th movement is possible re- 10 will be observed that when p I 'ltmdvesduwii i dleasr theg-pr, e at the upper end of the f Ewardly. as Sho n in t d 'flw 11 8 member Tliereiot'egcthe fiuidjat the exhaust side i q 59 will engage one side of lever}! eg id will resii- 5 d. ofnth normal exhaust pressure 'iently'iorce it in a. clockwise direction 6f fluid ast th metering Y pivot 43';

thus initiating' the efiectingmovement of' e t 1 operating piston 2ina reverse directionoflup fl. t e" al bi- "5 Y "L wardly as viewed: in th'e diam; 'During' sue i PM, 8 i movement the fluid atthe upp ri n f ton 1 V 'ly th'iough conduit'i'l'. Iii- 1. 'lilieftbmttieisq i 1 i 'mov'em t of piston thew; u H I W t eiid i'of cylindenriiis I discharges ii ;atniospheric"presu e s itctiveuponithe zupperw I @Wi r u $9 endpf pistonjl this istori will move upwardly; we??? #1 rapi'dlly uritiHt *the positic'n shown 'in the; wing? ""Su'cli "motion; "however, will= not" amt thepositionofleveilli which will remain in the position towhich it waspreviously moved rat of PM 9 llbli'll'b m condui new 0.wer. endgoffcvli id' thus-dvparent thet hi h or ppeg ifns by jr'ev'er e movement'dr the act'ua'tor piston ins- This veni aiicins. ,otayh s b M e uces h i efi ct ve re um. mm! p ston 53' xufl cientlyto some iorc the exoessi pressure at thatendQQ-Thg: 1'

timsiimeters nithepistonand the jpis n maintain piston 53 in its upper position until piston 2. completes its downward movement. From this point, the above described cycle of movement will be repeated.

It will be apparent from the above description and the accompanying drawing that a means for reversing a reciprocating fluid pressure motor at a. fixed point in its stroke has been provided and .only after its movable element has engaged and been stopped by a fixed abutment. This positively insures thatthe movable carriage or other device operated by the motor. will always change its direction of motion at exactly the same point in each cycle. This feature is of great value where very accurate cuts must be made by machine tools.

In addition, it will be noted that since the reversal oi. the operating piston 2 is effected upon an abnormal increase in the resistance to downward motion of that piston, the device will automatically reverse when the operating tool offers an abnormal resistance to motion. Thus if the piston 2 is used to drive a drill, the drill will be automatically withdrawn when the drill pressure becomes too great.

While there is illustrated and described only one form of the invention,.it is apparent that valve for reversing. the pressure and exhaust connections at the opposite ends of themovable element thereof, a cylinder having closed ends, a piston in said cylinder, one of said piston and cylinder members being stationary and the other movable and connected to said reversing valve for operating the latter, an open conduit connecting one chamber of the motor with one end of said cylinder, a second conduit connecting the other chamber of saidmotor with the opposite end of said cylinder, whereby the application of excess pressure to one chamber of said motor effects movement of the movable element thereof and also said piston in one direction respectively, means associated with the piston and, cylinder for preventing movement of said piston in the opposite direction when an excess pressure is applied to the other chamber of said motor until the movable element of said motor has completed its movement in the opposite direction, a lost motion connection between said piston and cylinder units and said reversing valve for preventing operation of said valve thereby in said first direction of movement, and means associated with said motor for operating said valve near the end of the movement of said motor ele-v open conduit connecting the opposite ends of said cylinders, the cross sectional areas of the second piston and its rod being so proportioned I that the normal operative pressure at said piston rod end of the second cylinder is 'insuflicient to overcome the normal exhaust pressure at the opposite end of said second cylinder, a reversing valve for said first motor adapted to reversethe pressure and exhaust connections at opposite ends of said first cylinder, and means associated with the projecting. end of said piston rod of the second motor for. operating said reversing valve.

3. In combination with a double acting fluid pressure motor including a piston, a cylinder and a reversing valve for reversing the'pressure and exhaust connections at opposite ends of said cylinder, means operatively connected to said reversing valve including a second fluid pressure motor having a piston and cylinder, a piston rod in said second cylinder, an open conduit connecting one end of said-first cylinder with the piston rod end of said second cylinder, a second open conduit connecting the opposite. ends of said cylinders, the cross sectional areas of the second piston and its rod being so proportioned that the normal operative pressure at said piston rod end of the second cylinder is insufficient to overcome the normal exhaust pressure at the opposite end of said second cylinder, a lost motion device in the connection between said second motor and said reversing valve for preventing operation of the valve by said second motorwhen said second piston moves toward its piston rod, but permitting operating in the opposite direction, and means associated wtih the first motorjo'r'shifting the reversing valve in the. direction in which it cannot be moved by said second motor when the piston of said first motor approaches the end of its travel in the direction toward said open conduit.

4. In combination with a double acting. fluid pressure motor including a cylinder, a piston in the cylinder and a reversing valve for reversing the pressure and exhaust connections at opposite ends of said cylinder, a second closed ended cylinder, a piston in said second cylinder having a piston rod projecting through one end thereof, a constantly open fluid pressure communication between one end of the first cylinder and one end of the second cylinder, a constantly open fluid pressure communication between the oppositeends of said cylinders, a restricted exhaust outlet for said opposite end of the first cylinder, a positive stop for said first piston in its movement toward saidopposite end of the first cylinder, the effective areas of said pistons being such that the pressure differential normally required to drive the first piston toward said opposite end of the first cylinder will be insufficient to shift said second piston from said one end of said second cylinder until the exhaust pressure at said opposite end of the first cylinder drops incident to engagement of said positive stop for the first piston, a lost motion mechanical connection between the projecting end of the piston rod of said second piston and the reversing valve effectiveto shift said reversing valve when the second piston moves from said one end of the second cylinder but ineifective to shift said reversing valve when said second piston moves in the opposite direction, and means for shifting said reversing valve in the opposite direction upon movement of said RALPH A. MILLERJ WILL E. monars. 

